While there is no dedicated thread on FT for the U.S.-based Chase/B.A. 2-4-1 Companion Voucher (although there should be), folks searching for relevant answers to their questions would be well served by following the thread for the U.K.-based Amex Companion Vouchers.... because the two programs are virtually identical. The Amex thread includes a well-developed wiki.
BA American Express 2-4-1 Voucher Discussion